The present invention relates to drilling subsea wells, and typically from a floating drilling rig. More particularly, this invention relates to a subsea riser disconnect equipment and techniques for sealingly connecting a lower riser extending downward into and fixed within a subsea well bore with an upper riser extending downward from the floating drilling rig, such that the upper riser may be disconnected from the fixed lower riser during adverse weather or other rig move-off conditions.
Subsea wells are increasingly important to hydrocarbon recovery operations. Numerous land-based wells have been drilled, but the percentage of hydrocarbons recovered from land-based wells is steadily decreasing in some parts of the world. Jack-up rigs have been used offshore for decades to drill wells subsea to recover oil, but jack-up rigs are practically limited to drilling operations in relative shallow water of several hundred feet. As water depth increases other drilling rig options may be required to facilitate drilling and well completion operations. In addition to an increase in the number of off-shore wells being drilled, in more recent years an increasing number of wells are being drilled in deeper water and at increasing costs. Accordingly, drilling from offshore rigs, e.g., drilling ships, semi-submersibles, jack-ups, drilling barges or submersible rigs has significantly increased in recent years. The economics associated with drilling offshore remains, however, a primary reason why more wells are not drilled offshore. Particularly, in drilling exploratory wells where financial risk and commercial hydrocarbon uncertainty may severely impact the economics for drilling such wells, costs and may be more critical in determining whether any wells are drilled at all, and how many may be drilled.
The majority of offshore or marine drilling rigs utilize riser sections as the outermost tubular between the rig and the seafloor, with the riser sections typically being bolted, clamped, mechanically fixed by dog-type latch mechanisms or otherwise connected. Riser sections conventionally include hydraulic lines spaced outwardly of the assembled riser pipe for operating the blow out preventer (BOP) and subsea ram stack located above the mud line. During an emergency or in anticipation of adverse weather conditions, the subsea BOP may be closed and the rams hydraulically activated to seal off the well bore. Prior to closing the rams, the drill pipe may be threadably disconnected above or below the BOP stack utilizing a back off tool or back off method, or the drill pipe may be sheared by the shear ram assembly. In some applications, acoustically or electrically activated subsea accumulators have been used to replace the hydraulic lines which commonly are run along side the riser pipe. The subsea BOP stack assembly used during deep water drilling operations may contribute significantly to the cost of drilling a well and a substantial amount of expensive rig time may be expended running in and removing the riser pipe sections and related well control equipment.
The above disadvantages associated with drilling from floating drilling rigs have long been known. Accordingly, some drilling or operating companies may recommend xe2x80x9criser-less drillingxe2x80x9d for certain deep water applications. A subsea pump may be provided to return the drilling fluid to the surface in a separate flow line. Riser-less drilling still has to contend with the high cost of the BOP stack and hydraulic operation of this equipment. Several wells have been successfully drilled from a floating drilling rig, while using a riser, wherein the BOP is placed on the drilling rig rather than subsea. To date, however, these wells practically are limited to geographic areas where and/or seasons when there is a reduced likelihood of adverse weather conditions which would require the floating drilling rig to relatively quickly disengage a portion of the riser, e.g., an upper riser from the lower riser. In these applications, however, elimination of the subsea BOP stack may result in significant cost savings when drilling a well. Further savings may be realized by using conventional threaded casing for a riser rather than flange-type riser pipe sections. Less area on the drilling vessel is required to store casing having the same nominal diameter as the riser pipe sections since conventional riser pipe sections include both flanges and hydraulic lines which are eliminated when using casing as the riser.
Typically, subsea BOP stacks are installed on the riser string. The BOP stack may be required to provide a subsea method of isolating a lower portion of the riser and well bore from the riser above the BOP stack. Stress in the riser typically includes the weight of the riser and the weight of the subsea BOP. Subsea BOP stacks may weigh in excess of 400,000 pounds. The weight of the BOP stack plus the weight of a riser sufficiently strong enough to deploy such stack and meet operational requirements necessitates that risers are inherently heavy pieces of equipment which may exert high levels of stress and strain on the drilling and on the riser sections. These effects may be even more pronounced in deep water applications. In deep water installations, installation of a typical riser system may require calm weather and well in excess of a week to install, and in excess of a week to retract. In addition to the subsea riser and BOP stack, electrical and hydraulic umbilical lines are typically deployed concurrently, to control and operate the BOP stack, choke and kill line valves, and hydraulic disconnects if present. Deployment and recovery of this equipment and the rig time involved all contribute significantly to well costs, as daily rental rates for semi-submersible drilling rigs may exceed $240,00 per day. Premature disconnection of a portion of the riser can likewise be expensive and time consuming, such as may be necessary in advance of hostile weather conditions, broken mooring chain or slipping mooring anchor.
If drill pipe is in a well bore and it becomes necessary to seal the interior of the well bore, pipe rams or shear rams in the BOP stack may be closed on the drill string to confine pressure and fluid within the well bore. In the event it becomes necessary to disconnect an upper portion of the drill pipe from a lower portion of the drill pipe, the drill pipe may be unthreaded at a tool joint, or cut with a chemical cutter or explosive charge. If pipe is stuck, the free point may be estimated by a free point calculation technique. Each of these disconnect methods requires time to determine free points, deploy appropriate tools on wire line, such as a xe2x80x9cstring shot,xe2x80x9d a free-point tool, a chemical cutter or jet-shot explosive charge. Multiple attempts and re-calculations may be required. The process can be time consuming and frustrating and may still result disconnecting at an undesirable disconnect point. Reconnecting after disconnecting can be even more exasperating, time consuming and expensive, and even impossible.
Disadvantages of the prior art are overcome by the present invention. An improved method of drilling from a floating drilling rig is hereinafter disclosed. A subsea riser disconnect is provided for connecting and disconnecting a lower riser from an upper riser.
This invention provides means and equipment for relatively quickly, physically disconnecting a floating drilling rig from a subsea well in a manner that may be operationally and economically more efficient than prior art equipment and techniques. In the event hostile weather conditions, rig conditions or well conditions threaten the safety or operating capabilities of an offshore drilling rig or work over vessel, the rig or vessel may be disconnected and moved out of harms way. The rig may later return to the well location and reconnect to the disconnected members. This invention provides means and equipment for installing a riser system and well control system which may provide for a more cost effective offshore drilling and/or work over operations than is available under prior art. Such improvements may reduce the costs to find, develop and produce hydrocarbons.
In one embodiment, this invention generally includes three primary components: a) a maritime or subsea riser disconnect for disconnecting and reconnecting an upper portion of the riser with a lower portion of the riser, b) a subsea riser valve for sealing off an interior of a well bore below the riser valve, and c) a drill pipe disconnect for disconnecting and reconnecting an upper portion of the drill pipe with a lower portion of the drill pipe.
Subsea Riser Disconnect
A preferred embodiment of a subsea riser disconnect includes an apparatus and means which disconnects an upper portion of the subsea riser from a lower portion of the riser, through axial movement of the upper riser relative to the lower riser. The upper riser and the lower riser may be collectively referred to as a riser system. The subsea riser disconnect may be positioned at substantially any point within the riser system, e.g., between the drilling rig and the mud line. The subsea riser is preferably accessible to either a remotely operated vehicle (ROV) or a diver, in order that a riser disconnect lockout device may be operated if needed. The subsea riser disconnect may facilitate placing the blow out preventer and well control stack (BOP) either on the rig or suspended from but relatively near the rig.
A preferred embodiment of a riser disconnect may include a male disconnect member secured to the lower end of the upper riser, and a female disconnect member secured to the upper end of the lower riser. The male disconnect member may include a seal mandrel and seal elements for providing a hydraulic seal between the male disconnect member and female disconnect member. The male disconnect member may also include a collet mechanism to facilitate latching and unlatching the male and female disconnect members. A lockout device may be included to prevent inadvertent actuation of the subsea riser disconnect, such as during initial installation of the riser disconnect and riser system. Manipulation of the lockout may be externally performed, such as by ROV, diver or otherwise.
The female riser disconnect member may include a seal bore receptacle for sealingly receiving the seal mandrel within the seal bore receptacle, and a circumferential collet groove may be included in an inner surface of the female riser disconnect for engaging collet dogs. A conical shaped entry guide may be included on an upper end of the lower riser disconnect member to guide the male disconnect member into the female disconnect member during subsea connection of the male and female disconnect member.
Manipulation of the riser disconnect latch may be performed by axial motion or reciprocation of the upper riser relative to the lower riser. (The terms xe2x80x9caxial reciprocation, reciprocation, axial motion, axial, or similar variations of these terms, as used herein may be defined to be substantially synonymous, and include linear displacement of a first component relative to a second component, substantially along a common linear axis, in a first direction and/or second direction, but not necessarily consecutively in both directions during a single manipulation period.) The latching collet mechanism of the riser disconnect may be manipulated between the collet latch position and the collet unlatch position by alternately applying tension and releasing tension in the riser disconnect by the drilling rig.
In an initial installation, the riser latch mechanism, including the collet mechanism, may be positioned in the collet latch position. After the riser system is installed and cemented in position within the well bore, tension may be applied to the riser system at the riser disconnect to securely retain the latched engagement between the male and female disconnect members.
To disconnect the male and female disconnect members, such as in advance of an approaching storm, tension in the riser disconnect may be relaxed allowing the male disconnect member to move axially downward relative to the female disconnect member, thereby unlatching the collet mechanism. The upper riser may be subsequently raised, separated from and suspended above the lower riser. The rig may then be moved and/or the upper riser recovered to the rig.
To reconnect the riser disconnect, the male disconnect member may be guided by the entry guide into engagement with the female disconnect member and the collet mechanism re-latched. Tension may be applied and maintained in the riser system to retain the latched configuration during operations until it is desirable to again disconnect the riser disconnect system. Upon completion of well work operations, the female disconnect member with the male disconnect member (plus a subsea riser valve, if run) may be typically recovered together by normally cutting the riser below the mud line with either an explosive charge, a chemical cutter or a mechanical cutter.
If desired, the riser disconnect and lower riser may be drilled into position in the sea bed while the well bore for the lower riser is being drilled. This may be accomplished by a number of means, for example preferably by positioning the lower riser on the sea bed with a riser disconnect and portions of an upper riser attached or to be attached substantially during drilling operations, and running a string of drill pipe, a drill bit and/or an under reamer bit through the deployed riser assembly and rotating the riser string with the bit while drilling the lower riser into the seabed. Alternatively, the drill string may substantially swivel or rotate within the riser while the riser may not rotate or may rotate independently from the drill string, while drilling the lower riser into the sea bed for cementing and permanent placement of the lower riser. The drill bit and drill string may then be retrieved back to the rig. Those skilled in the art of well drilling operations will appreciate that there are a number of other means for drilling in the lower riser. An alternative embodiment for the riser disconnect provides non-rotational engagement grooves in order to rotate the riser with the drill string.
In an another alternative embodiment, the upper riser may include the female disconnect member and related components, while the lower riser provides the male disconnect member and related components. An alternative embodiment may also provide the seal members within the female member while the male seal member provides a substantially smooth sealing surface on a mandrel.
It is an object of the present embodiment to improve the economics of drilling, completion and work over operations from an offshore rig by providing a more economical method of equipment optimization and use. An embodiment provides apparatus and means for placing the wellhead and BOP system substantially on the rig. In a preferred installation, a riser system may be utilized which employs riser joint connections secured by means and apparatus other than by flanges and bolting, such as a threaded riser consisting of joints of well casing, or a groove locked connection. Such equipment usage and arrangement may also save a considerable amount of time in retracting and deploying the upper riser. In addition, a flex joint may be provided either above or below the riser disconnect to accommodate riser angular displacement.
It is also an object of this embodiment to provide apparatus and means to relatively quickly disconnect an upper riser from a lower riser to facilitate moving the rig out of harms way. This embodiment provides a riser disconnect system which may be actuated by merely reciprocating the upper riser relative to the lower riser.
It is further an objective of this embodiment to provide a riser disconnect apparatus which may be easily and reliably manipulated from the rig. Manipulation of the riser disconnect between the riser latch position and the riser unlatch position may be performed by simple axial reciprocation of the riser disconnect from the rig. Moving the BOP stack near the rig may also assist in economic riser deployment and recovery.
It is a feature of this preferred embodiment to provide a riser disconnect system which may be reconnected after disconnecting the male and female disconnect members. The riser disconnect system of this embodiment may be repeatedly connected and disconnected.
It is another feature of this embodiment that the riser disconnect may be manipulated between the connected and disconnected positions without subsurface hydraulic and/or electrical umbilical lines. Although such lines may optionally be employed for other purposes, the riser disconnect does not require them.
It is also a feature of this embodiment that the riser disconnect system may be locked in the riser latch or unlocked from the riser latch position. The riser system, including the riser disconnect may be installed while the riser disconnect is locked in the latched position, and after installation the riser disconnect may preferably remain unlocked, while riser tension maintains the disconnect in a latched configuration.
These advantages may enhance deep water operations by facilitating employment of an improved, more cost effective riser and drilling system which may save considerable time and costs. The subsea riser disconnect may provide for placing the BOP stack on or suspended just below the rig or drill ship, thereby effectively eliminating placing the BOP stack on the ocean floor. By minimizing the number of subsurface hydraulic and electric umbilical lines, connectors, and kill and choke lines, several days of rig time may be saved. The preferred drilling equipment configuration and alternative embodiments thereof, as disclosed herein, may be particularly applicable for drilling and completing exploratory or other wells where well costs are a key consideration and where the well may not be intended for production after well testing.
It is also a feature of this embodiment that the riser disconnect system may be employed with re-entry risers as well as drilling and completion risers. Although the preferred embodiment is illustrated generally in terms of use with a drilling riser installation, the concepts and apparatus for riser disconnect manipulation by axial reciprocation methods may be applied equally well to risers used in completion and re-entry operations following well completion.
Subsea Riser Valve
A preferred embodiment of a subsurface riser valve includes an apparatus and methods for sealing the interior of a well bore, below the riser valve, through axial movement of the riser above the riser valve (generally, the upper riser) relative to the riser below the riser valve (generally, the lower riser). The subsea riser valve may be positioned at substantially any point along a riser system, preferably below the riser disconnect such that the riser valve may be closed in conjunction with or prior to disconnection of a riser disconnect. The subsea riser valve may also provide a subsea method of well control, such that the BOP stack may be positioned on the rig.
A preferred embodiment of the subsurface riser valve provides for the riser valve as a distinct, stand-alone piece of equipment which may be employed separately or in combination with riser and/or drill pipe disconnect apparatus. The riser valve is preferably used in combination with the riser disconnect, such that the riser valve is positioned below the riser disconnect in order that the interior of a lower riser and well bore below the riser valve may be hydraulically isolated and confined. The lower end of a riser valve may be sealingly connected to the upper end of a lower riser, a well casing, a well head or other subsea component. The upper end of the subsea riser valve may be directly or indirectly secured to the lower end of the subsea riser disconnect.
The subsea riser valve includes a valve housing enclosing a valve sealing member, and a valve actuation mandrel telescopically extending from the upper portion of the riser valve. A linkage or connector may moveably connect the valve sealing member and the valve actuation mandrel. The riser valve may be biased closed and may be opened in response to axial tension in the riser system. A lockout device similar to the lockout device described on the riser disconnect above, may be included with the riser valve apparatus, to lock the riser valve in either the valve opened or valve closed positions.
The riser valve may be locked in the opened position during installation of the riser system to allow the riser to fill with fluid and to allow circulation of fluids or slurries through the string prior to applying tension in the valve system. When the riser valve and riser system are properly positioned, installed and cemented, tension may be exerted on the riser valve to maintain the valve sealing member in the valve opened position. Prior to closing the valve sealing member, components within the through bore of the riser valve may be removed from within the through bore of the riser valve, such that the valve sealing member may freely move between the valve closed and valve opened positions.
It is an objective of this embodiment to provide an apparatus and means for sealing the interior of a riser and well bore below the riser in response to axial motion of the upper riser string. To close an opened valve sealing member, axial tension in the riser system may be relaxed such that the weight of the riser and the resulting closing biasing force may close the riser valve, effectively sealing the well bore below the riser valve. To open the riser valve, axial tension may be applied to the upper riser and valve actuation mandrel sufficient to overcome the riser weight and closing bias force. The riser valve may be opened and closed repeatedly as needed during well operations.
It is an object of this embodiment that the riser valve may be used in conjunction with the riser disconnect to provide a mechanically actuated riser disconnect and well control system for connecting a drilling rig to a subsea well bore. Such mechanically actuated system may assist in facilitating placing the BOP stack and related well control equipment on or near the drilling rig. Such arrangement may significantly decrease well costs by eliminating hydraulic and/or electrical umbilical lines between subsea equipment and the rig. Concurrent and subsequent axial movement of the riser may also unlatch and disconnect the upper riser from the lower riser. The rig and upper riser may thereafter be removed from the situs of the well, while the subsea well control valve remains to contains well pressure and fluids within the well bore.
It is also an object of this embodiment to provide a subsea riser valve which may be manipulated between the opened and closed positions without hydraulic or electrical lines. Mechanical movement within the valve mechanism is provided by axial movement of the riser system, thereby effectively eliminating the need for hydraulic or electrical actuation of the valve sealing member.
It is a feature of this embodiment that the riser valve provide a full bore opening through bore. The preferred riser valve, including the valve sealing member may provide an ID that is not less than the minimum ID of either or both of the upper riser and lower riser.
It is another feature of this embodiment that the preferred riser valve may be provided as a separate, stand alone device, such that the riser valve may be used alone in a riser system, or a riser disconnect may be combined with a stand-alone riser valve and/or other separate devices. Alternatively, the riser valve may be integrated into a common housing with a riser disconnect apparatus. Both apparatus may be compatible for use as an integrated tool combining both the riser valve and the riser disconnect in a common housing or body, as both may be compatibly manipulated by axial tension applied at the drilling rig.
It is also a feature of this embodiment that the riser valve may be installed inverted from the preferred orientation described above, such that the valve actuation mandrel is connected to the lower riser, casing or well head. In either the preferred or an inverted embodiment, the riser valve may be manipulated with tension in the upper riser.
An additional feature of other embodiments of this invention is that the riser valve components may be varied such that the valve sealing member may be of a type other than a ball type sealing member, such as plug type rotational cylinder members, or gate type sealing members, or flapper type sealing members. Alternative embodiments for a riser valve may be configured for manipulating each of these types of sealing members from axial movement of the upper riser relative to the lower riser.
Drill Pipe Disconnect
Apparatus and method are disclosed for connecting and disconnecting an upper portion of a drill pipe string above a drill pipe disconnect apparatus from a lower portion of a drill pipe string below the disconnect apparatus. The drill pipe disconnect may be positioned at substantially any point along the drill string wherein it may be convenient or desirable to disconnect a portion of the drill pipe string from the remainder of the string. Such disconnection may be required in conjunction with disconnecting a subsea riser disconnect, and/or in conjunction with closing a subsea riser valve, such as may be desirable in advance of relocating the rig due to approaching threatening weather.
The drill pipe disconnect is preferably used in conjunction with the subsea riser disconnect and/or the subsea riser valve. Prior to closing a riser valve and/or disconnecting a riser disconnect, rather than pull the entire string of drill pipe above the riser valve, it may be prudent to temporarily abandon the portion of the drill pipe string which is below the riser valve and the drill pipe disconnect. In such event, the drill pipe disconnect may be disconnected at a point below the riser valve, and the upper disconnected portion of drill pipe pulled up to above the riser valve, such that the riser valve may be closed and the riser disconnect subsequently disconnected.
The drill pipe disconnect may be selectively operable to mechanically disconnect or connect the upper and lower portions of a drill pipe string, in response to movement of a latch mechanism, while also providing axial and rotational strength commensurate with the strength of the drill pipe in use. Non-rotational engagement components may be included within the drill pipe disconnect to carry rotational stresses in the drill string.
A preferred embodiment of a drill pipe disconnect apparatus may generally include a male drill pipe disconnect member and a female drill pipe disconnect member. The male disconnect member may include a collet mechanism to latch and unlatch the male and female disconnect members. A latch sleeve may be included, which is movable between a collet latch position and a collet unlatch position. When the latch sleeve is in the collet unlatch position, the male drill pipe disconnect member may be released from engagement with the female drill pipe disconnect member.
The male and female disconnect members of the drill pipe disconnect may be secured within a drill pipe string by connections provided on each end of the drill pipe disconnect. In a preferable embodiment, the upper end of the male disconnect may include a threaded box type tool joint, while the lower end of the female disconnect may include a threaded pin type tool joint.
A preferred method of operation for the drill pipe disconnect generally includes providing and operating a first assembly and a second assembly, which is a modification of the first assembly. The first assembly may typically be employed for an initial drill pipe disconnect installation. Thereafter, subsequent to disconnecting the drill pipe assembly and recovering the male drill pipe disconnect member to the rig, the second assembly may be installed. The second assembly is provided by substituting a male reconnect member for the male disconnect member, to reconnect the male reconnect member with the female disconnect member. Thereafter, if desired the male reconnect member and the female disconnect member may be re-unlatched from one another.
The first assembly for the drill pipe disconnect may be installed in a drill pipe string, such that the collet mechanism and latch sleeve are in the collet latch position. A shear pin may secure the position of the latch sleeve within a male disconnect housing, in the collet latched position. The string of drill pipe including the drill pipe disconnect may be repeatedly inserted into and withdrawn from a well bore as needed, such as when xe2x80x9ctripping pipe,xe2x80x9d with the drill pipe disconnect apparatus threadably secured within the drill string.
In the event it becomes desirable to disconnect the drill pipe disconnect and temporarily or permanently abandon a lower portion of drill pipe within the well bore, an unlatching ball or other closure device may be dropped through the upper portion of drill pipe, from the rig floor. The unlatching ball may sealingly seat on the unlatching seat such that hydraulic pressure may be applied to the drill string from the rig to cause the latch sleeve to shear the shear pin and move downward to a position where the collet dogs may unlatch from engagement with the female disconnect member. The male drill pipe disconnect member may then be telescopically withdrawn from the female disconnect member, and the male disconnect member and upper portion of drill pipe withdrawn to the rig.
To reconnect the male disconnect member with the female disconnect member, the male second assembly of the male disconnect member may be provided with a positionable latch sleeve that includes two unlatch grooves, shear pins that provide for two shearing actions, a latching seat and an extension tube on the latch sleeve. The male disconnect member may subsequently be engaged with the female disconnect member in the well bore. A latching ball may then be dropped through the drill pipe string for sealingly seating on a latching seat in the latch sleeve. The latching seat may be secured within the latch sleeve by shear pins. Hydraulic pressure may be applied within the drill string, sufficient to shear the double shear pins at a first shear point. The latch sleeve may then move downward from a collet unlatch position to a collet latch position, such that the male and female disconnect members are again securely latched together.
Hydraulic pressure within the drill string may be further increased to until the shear pins which secure the latch seat within the latch sleeve are sheared, allowing the latch seat and latching ball to be ejected downward from within the latch sleeve. The extension tube on the latch sleeve may receive or catch the ejected latch seat and latching ball. The extension tube may provide a plurality of ports to hydraulically interconnect the upper and lower portions of the interior of the drill pipe. A hydraulic conduit is thereby provided through the drill pipe through bore such that fluid may be circulated through the upper and lower portions of the drill pipe string. The latch seat and latching ball may remain within the extension tube. As an alternative, instead of shearing the latch seat pins and ejecting the latch seat and latching ball and receiving the latch seat and latching ball within the extension tube, the latch ball may be recovered to the surface. Fluid may be circulated down the drill pipe/casing annulus and back up through the drill bit and drill pipe to reverse flow the latching ball back to the surface of the rig.
In the preferred embodiment, to re-unlatch the male drill pipe disconnect from the female drill pipe disconnect, a re-unlatching ball may be dropped for sealingly seating on a re-unlatching seat. Hydraulic pressure applied within the drill pipe through bore may shear the double shear pins at a second point and allow the latch sleeve to move downward to a re-unlatch position, wherein the male disconnect member may be withdrawn from the female disconnect member and recovered to the rig. For subsequent re-engagement, the male disconnect member may be again re-dressed as described above for reconnection.
The drill pipe disconnect apparatus and/or method may be utilized in either an off-shore installation or a land based installation. In a land based installation, the drill pipe disconnect may provide for a disconnect point in the drill pipe string, such as may be desirable to provide above a geologic trouble spot or near a casing seat above an open hole section. It may be desirable to provide a convenient disconnect device at a point in the drill string where backing off or disconnecting otherwise may be difficult or impossible to achieve, particularly in deep wells or along long horizontal well bore sections.
It is an object of this embodiment to provide a method of operation and an apparatus for disconnecting an upper portion of a drill pipe string from a lower portion of the drill pipe string in a quick, reliable manner. The preferred disconnect method and apparatus disclosed herein facilitates providing a relatively simple and reliable disconnection point within a drill pipe string. Some of the components and mechanisms relied upon for operation of this embodiment are recognized as generally reliable mechanisms, such as a collet mechanism, shear pinned components, and ball and seat type hydraulic seals.
It is also an object of this embodiment to provide a drill pipe disconnect apparatus and method which may be manipulated without relying upon back-off tools, back-off methods, external manipulation devices or destruction of drill pipe to disconnect. This embodiment provides method and apparatus for disconnecting an upper section of a drill pipe string from a lower section of the drill pipe string by dropping a ball and applying hydraulic pressure to unlatch a latch mechanism. The drill pipe disconnect can also be actuated with a portion of the drill string off the bottom of the well bore. To disconnect the drill pipe disconnect mechanism with the drill string off bottom of the well bore, disconnection may only require that a higher pressure be applied to the interior of the drill pipe string above the dropped ball.
It is a feature of this embodiment that an apparatus and method are provided for reconnecting the upper and the lower drill pipe sections after they have been disconnected. In this embodiment the upper and lower drill pipe sections may be re-engaged and then re-latched by dropping a ball and applying hydraulic pressure to securely re-latch the upper and lower drill pipe sections.
It is also a feature of this embodiment that the re-latched drill pipe sections may subsequently be unlatched again, thereby facilitating repeated disconnects and reconnects as desired. The drill pipe reconnect and disconnect apparatus and methods are simple and reliable to operate and may save time and costs in disconnecting a drill pipe string at a pre-determined location.
It is yet another feature of this embodiment that the drill pipe disconnect may provide an apparatus and method for rotating the drill string. Non-rotational engagement members are provided which may provide rotational strength within the disconnect apparatus which is substantially equivalent to the strength of the drill pipe.